Why am I saying all this? To make it clear that yes, Ma Long is a far better player. But the gap is more cognitive and experience based than technical.
I think you are not absolutely right on that.
My impression is that a lot of people call Aruna's technique inferior because it is not common. It does not look how you would describe a perfect topspin. However, the key elements such as acceleration in hitting point, power, spin they are all there. Consequently, the technique cannot be bad. Otherwise his shots wouldn't be as effective and powerful as they are. That he has some uncommon moves before and after hitting the ball doesn't matter if he has enough time to get ready for the next shot. So finally, his technique is not worse than of most European players. As you said Boll's technique is far from optimum as well and probably it is one of the better ones in Europe.
But I don't agree with you saying that there is no big technical gap between Chinese players or some other world class players and Aruna. It definitely is. For instance, if you look at Ma Long he always is in the right position, has balance and consistency. It looks as if one shot flows smoothly into the next. Also, his technique is effective in terms of energy consumption. It's similar for all CNT players. In contrast with this, I often get the impression that Aruna almost trips over his own feet. He often lacks stability and is playing on one feet, next to his head or in front of his belly. Every stroke looks different. Of course, in most of the cases he is able to compensate these technical faults with an unbelievable power and athleticism. What makes it more impressive in my eyes. He often has little stability but plays a very hard stroke. Maybe, this is his strenght and weakness at same time because he plays out of such uncommon positions that his opponents are surprised and cannot believe it. Moreover, they are not used to the curve of his uncommon (or unorthodox) technique. Probably, if they play him second or third time they look much better against him. Your argumentation that he only needs some practice with CNT players to adapt to their speed is subjective. I could argue as well that players like Boll or CCY only need some practice with him to adapt to his special style and then he has no more chance to win against them because they have much more variation and experience. They are more complete players.
You cannot overlook that he has some instability and inconsistency only because he compensates it with will, athletics and fighting. It is as someone said before: he plays more like one stroke after another. Playing one and then thinking about the next. Not like Ma Long playing a whole combination. But these combinations are also part of technique.
It's the same with his footwork. Aruna is very, very, very fast. He has so much power in his legs that he can reach almost every ball. Besides this physical strength, as mentioned before, he has this rare talent to play fantastic strokes even if he is not in the best position. And that is one impressive part of his game (and technique if your definition includes that). However, in terms of technique his footwork is bad. It seems as if the lacks some kind of coordination. Examples: standing on one foot, stumbling, moving looks more than this of a 100 metres sprinter than of a table tennis player, weight on the wrong foot, ... In my opinion, this is also the reason why he has no chance against Ma Long and CNT. They are playing that fast that he is not able anymore, to compensate his technical faults in footwork with his physical strength. When Ma Long was blocking down the line in his FH or playing counter topspin he sometimes wasn't even able to make one further step in that direction. Not only because Ma Long played faster than he is used to, but also because his technique crashed at that speed. And I think it is not enough to practice with higher speed or against Hurricane rubbers. To be competitive with Ma Long he would have to change technical aspects of his game. Because with his current style there is a limit of how much speed he can handle.
As I said before I am not saying that his technique is bad. That's not what this paragraph is about. It is great and not worse than most other players. Most players have similar problems facing the CNT. But saying that there is no big gap to Chinese technique is ridiculous in my eyes. CNT members are not only playing faster because of their rubbers. The rubbers might have an impact but it is also because they have a better technique. I had three Chinese coaches during my life. All of them had so much more knowledge about technique than every German coach I met. It was unbelievable.
Anyway, all that doesn't matter because technique isn't everything. Putting all factors together (tactics, technique, physical strength, will, nerves, ...) Aruna is a very good player. He improved a lot - especially his backhand and receives - and had some fantastic performances at Rio. Thus, his great results were well-deserved. He has a fresh style of playing and the spectators like him a lot. Therefore, I hope he will play on that level more often. I enjoy watching him.
Refering to the beginning of the thread: this is no cultural or African thing. It is his personal style and it has nothing to do with 40+ ball.